This Mentored Research Scientist Development Award application describes training and research plans designed to qualify the candidate for a career as an independent mental health researcher with expertise in the implications of co-morbid psychopathology for the etiology, classification and treatment of eating disorders. Unrecognized systematic heterogeneity within the population of individuals with eating disorders may produce inconsistent findings across studies (e.g., if heterogeneous subgroups are entered in different proportions in different studies) and obscure clinically relevant information about etiology, prognosis and treatment response. In this application, the research plan focuses on understanding how heterogeneity in patterns of co-morbid mood and anxiety psychopathology is related to treatment response in patients with anorexia nervosa (AN). To this end, the underlying structure of mood and anxiety disorder co-morbidity will be examined in 150 AN patients using dimensional measures of psychiatric symptomatology and temperament. Participants will be assessed 1-2 weeks after admission for acute (i.e., inpatient or day hospital) treatment at a large, well established specialty care program and then followed closely for 12 months after discharge to determine whether co-morbidity subtypes have utility for identifying predictors of treatment response in AN. Guided by an interdisciplinary team of mentors, advanced training in 1) clinical and etiologic factors relevant to research with AN patients; 2) dimensional approaches to the study of psychopathology; and 3) data analytic techniques for identifying clinical subgroups and modeling longitudinal outcomes will facilitate the candidate's goal of establishing an independent research career focusing on the psychopathology and treatment of AN. Information about differences among AN patients with respect to mood and anxiety disorder symptoms and personality traits will promote treatment development initiatives by identifying potential targets for novel interventions. Further, a better understanding of factors related to negative outcome during the period immediately following discharge from acute treatment may lead to the development of more effective treatments and relapse prevention programs. Finally, understanding robust differences in symptom patterns among patients with AN may provide clues that will promote research on the complex causes of this pernicious disorder.